The objective of this project is to determine those factors that control blood flow to the uterus. This includes elucidation of physiologic control mechanisms in non-pregnant and pregnant uteri and determination of the effects of pathologic stimuli and pharmacologic agents on the uterine vasculatures. Uterine blood flow will be measured with electromagnetic flowmeters and distribution of blood flow to individual uterine tissues will be determined by isotope-labelled microspheres. Uterine and systemic vein levels of ovarian hormones will be correlated with blood flow during the ovarian cycle and early pregnancy. Estrogen cytosol receptors will be measured at different phases of the estrogen-induced uterine blood flow response.